Petroleum systems of the Zhu III subbasin, Pearl River Mouth Basin, South China Sea

The Zhu III subbasin is one of three subbasins in the Pearl River Mouth Bas in in the northern shelf of the South China Sea. The Zhu III belongs to a r ift basin initiated in the Paleogene, being a part of the rifting lake grou p of Paleogene age in the Pearl River Mouth Basin, The evolution of the Zhu III subbasin can be divided into three stages. lacustrine facies of the ea rly stage (Paleocene-middle Oligocene), bay facies of die middle stage (lat e Oligocene), and open shallow marine of the late stage (Neogene), forming, respectively; source, reservoir, and seal rocks. The lacustrine sediments include the Wenchang Formation (oil source rock) and the Enping Formation ( Sas source rock), which are die source rocks of two petroleum systems in th e study. area. The Zhu III subbasin experienced three obvious tectonic move ments, of which the tenso-shear movement in the late Oligocene and extensio nal movement at the end of the middle Miocene formed the main oil-bearing s tructures in the study area. Oil and gas exploration results, synthetic stu dy of geochemical and thermal modeling of the two source rocks, diagenesis and organic inclusions, and basin modeling show that there are tno petroleu m systems in the Zhu III subbasin, the Wenchang-Zhujiang(.) petroleum syste m in Wenchang B sag, and the Enping-Zhuhai(.) petroleum system in the Wench ang A sag. In the two petroleum systems, hydrocarbon generation, migration, and accumulation peaks are late Miocene-Holocene.